The occlusion of the arteries can lead to insufficient blood flow resulting in discomfort and risks of angina and ischemia. Significant blockage of blood flow in the coronary artery can result in damage to the myocardial tissue or death of the patient. In most cases, occlusion of the artery results from progressive long term deposits of plaque along the artery wall. While such deposits may be concentrated and occlude the artery at a particular site, the deposits are most certainly present throughout the arteries and the vascular system.
Coronary artery bypass graft (CABG) surgery is a surgical procedure performed in severe cases of coronary blockages. CABG procedures involve anastomosing an artery to a vascular graft which restores the flow of blood by establishing another pathway around the occluded vasculature. During coronary artery bypass graft surgery, a vein or other conduit can be attached proximally to the patient's aorta. The other end is attached to the blocked artery, downstream from the obstruction, thus bypassing the coronary occlusion. CABG procedures can be done by placing the patient on a heart-lung machine and stopping the heart from beating or they can be done on a beating heart without a heart lung machine. One problem encountered in either CABG procedure is the need to perform the procedure, while simultaneously maintaining sufficient function of the patient's circulatory system.
In the case where a CABG procedure involves arresting the heart so that blood flow is diverted from the vessel to be anastomosed, the patient's blood circulation is maintained by a cardiopulmonary bypass (CPB). This bypass is accomplished by diverting the blood flow at selected arterial locations. The blood is diverted to the bypass system for release of carbon dioxide and subsequent oxygenation. Then, the blood is returned to the patient via a pump. Examples of these procedures are found in U.S. patents: U.S. Pat. No. 5,799,661 to Boyd, et al. which discloses a device and method for performing CABG surgery for multi-vessel coronary artery disease through port-access or closed-chest thorascopic methods; and U.S. Pat. No. 5,452,733 to Sterman, et al. which discusses performing grafts with an efficacy equal to or greater than conventional open surgical bypass techniques.
Although the beating heart CABG procedure eliminates the need for CPB, it has required diverting blood flow for a proximal anastomosis, such as one which attaches graft material (e.g., a graft vessel) to the ascending aorta. To attach the graft to the aorta in a beating heart situation, surgeons have typically used a “side-biting clamp” that isolates the aortic region where the anastomosis will be performed. This allows the surgeon to create the anastomosis without the site being exposed to the high-pressure blood flow of the normal aorta.
Among the drawbacks associated with aortic clamping are an increased chance of trauma to the arteries caused by ligatures at the clamped site and the possible dislodging of plaque within the clamped vessel wall. As mentioned above, the arterial bypass may be required due to the deposits of plaque which have occluded the vessel. However, the plaque is typically present throughout the artery and is not limited to the occluded location. Clamping the artery creates a risk of plaque being released into the blood stream. This release of plaque has the potential of causing a stroke, occlusion of a smaller peripheral vessel, or other vascular trauma. In a beating heart procedure, full clamping (i.e., cross clamping) of the aorta for graft attachment at the proximal anastomosis is not feasible. Therefore a side biting clamp is used to clamp off only a portion of the cross-section of the aorta, where the proximal anastomosis is performed. This type of clamping procedure poses the same risks described above with regard to cross clamping, e.g., the risk of release of plaque and resultant cause of a stroke, occlusion of a smaller peripheral vessel, or other vascular trauma.
Other attempts to address the problem related to blood flow diversion include diverting the blood by placing a balloon catheter within the aorta, such as described in U.S. Pat. No. 5,868,702 to Stevens, et al., for example. Drawbacks of using a balloon catheter in creating a seal to divert blood flow include the possibility of disturbing plaque deposits and creating particles in the blood stream, the chance that the balloon catheter may move within the aorta disrupting the seal and resulting in blood loss, and trauma to aortic tissue caused by the pressure needed to create the seal.
There remains some concern in the surgical community that neurological defects and strokes are associated with the use of heart-lung machines, side-biting clamps, and balloon occlusion devices.
PCT Patent Application No. PCT/US98/10245, to Cardio Medical Solutions and to Nobles, et al., which published under Publication No. WO 98/52475, attempts to address problems associated with diverting blood flow. Nobles, et al. provides a method and device for creating an area of hemostasis within a blood vessel without interrupting the flow of blood through the vessel which eliminates the need to clamp the vessel. However, the Nobles, et al. device requires the withdrawal of the hemostasis device prior to obtaining a tight seal between the graft and vessel. Therefore, since the area of hemostasis is lost upon the retrieval of the hemostasis device, the artery is open and blood is lost until the sutures are tightened.
Yet another problem related to CABG procedures lies in the procedure of suturing the vessels to create a tight seal. To ensure the integrity and patency of the anastomosis, the graft and vessel to be joined thereto must be precisely aligned with respect to each other. If one of the tissues is affixed too close to its edge, the suture can tear through the tissue and impair both the tissue and the anastomosis. Another problem is that, even after proper alignment of the tissue, it is difficult and time consuming to pass the needle through the tissues, form the knot with the suture material, and ensure that the suture material does not become entangled. These difficulties are exacerbated by the small size of the artery and graft. Another factor contributing to the difficulty of the CABG procedure is the limited time available to complete the procedure. The surgeon must complete the graft in as little time possible due to the absence of blood flowing through the artery. If blood flow is not promptly restored, sometimes in as little as 30 minutes, the tissues the artery supplies may experience significant damage or necrosis. As mentioned above, surgeons are under pressure to reduce the cross-clamp time, yet, an incomplete suture may result in a leak in the tissue approximation between the vessel and graft. Moreover, the tissue approximation must be smooth and open. Hence, the suture cannot be hastily performed.
Additionally, the difficulty of suturing a graft to an artery using minimally invasive surgical techniques, where the surgeon uses ports to access the internal organs to perform the procedure, has effectively prevented the safe use of complicated suturing technology in cardiovascular surgical procedures. Accordingly, many procedures are performed invasively and require a sternotomy, an opening of the sternum. As a result, the recovery times for patients is significantly increased. U.S. Pat. No. 5,868,763 to Spence, et al. attempts to circumvent the suturing process by attaching the vessels to a cuff device. Spence, et al. utilizes a passageway for continued blood flow so there is no clamping of the artery.
Arcia, et al., in U.S. Pat. No. 6,358,258, describes systems and methods for performing anastomosis or attachments of body ducts, which are asserted to simplify suture delivery in both stopped heart and beating heart procedures and to be suitable for use in a minimally invasive environment using percutaneous ports, or with retractor systems or in a generally open surgery environment.
Houser, et al., in U.S. Pat. No. 5,989,276, discloses various devices and techniques for performing bypass, one of which includes a device which can be intralumenally originated. Various other clamping arrangements are provided for securing a graft to a vessel without the use of sutures or other fasteners.
In PCT Application No. PCT/GB01/04666, to Anson Medical Limited and to Hopkinson, et al., and which published under Publication No. WO 02/34143, apparatus is described for carrying out an anastomosis by sealing an arteriotomy and connecting a graft to the artery with the seal in place (see the Abstract). The apparatus includes means for sealing the hole and means for locating the graft on the outside of the wall of the artery. Once the graft is completely connected, the seal can be removed from the artery through the bore of the graft. Means may be provided for clamping the graft and seal in place while the graft is being connected to free both of the surgeon's hands for the connection operation.
The problems discussed above can be exacerbated in those cases where a multiple anastomosis is required. In those cases where multiple bypass procedures are performed, the patient will naturally be subject to increased risks as multiple grafts must be sutured to perform the bypass. Therefore, there is a need to improve and simplify anastomosis procedures.